Various dispensing devices have been developed where it is desirable to provide information about the number of discharges of a particular substance that have been dispensed from or remain in a container. For example, various aerosol dispensing devices have been developed that include a dose indicating device to indicate the number of metered doses that have been dispensed from the device, or to indicate the number of doses remaining therein. For example, patients have certain conditions that can be treated with medicaments dispensed in an aerosol and administered to the patient by inhalation. In one format, the aerosol with medicaments are contained in a container, and dispensed in metered, or measured, dosages with an inhalation device, or actuator boot. In such an arrangement, it can be important for the patient to be able to ascertain the number of metered doses remaining in the container, either by an indication of the number remaining therein or by knowledge of the number already dispensed therefrom, such that the patient is not caught unaware with an empty container when in need of the medicament. Thus, it may be important for the inhalation device to provide an accurate indication of either the number of doses remaining in the container, or the number of doses already dispensed therefrom.
In order to provide an accurate indication, some devices are provided with a dose indicator secured to an end of the container, with an actuation force being applied to the dose indicator so as to actuate the dose indicator and the container. In such a system, the force required to actuate the dose indicator must be tuned such that it is not greater than the force required to actuate the container, which could result in an uncounted actuation. Conversely, the force required to actuate the dose indicator cannot be so minimal as to count an actuation when such an event has not transpired.
Some dose indicator devices include a first member (e.g., a cap member) moving along an axis relative to a second member (e.g., a base member secured to the container) in response to a force applied to the first member. In some embodiments, one of the cap or base members has a center post received in a corresponding socket of the other member. If the force applied to the first member is radially spaced (off-center) from the axis, the first member may tilt relative to the second member, which can then cause an increase in friction, for example along the center post or between nested, circumferential walls of the first and second members. This friction force, in turn, increases the force required to actuate the dose counter, which may then not be tuned with the actuation force of the corresponding container. Likewise, an off-axis force application and associated tilting of the cap member can cause the geometrical relationship between internal components, such as ratchet/pawl mechanism, to change, thereby delaying the actuation, which can also adversely affect the relationship between actuation of the container and of the dose indicator. As such, the need remains for an actuator that minimizes the adverse impact from off-axis force applications.